Microphone



March 30 1926.

W. L. WALKER MICROPHONE Filed August 12, 1921 mil/Var.

2H3 his flttozmm s units STA T E rarestseries WILLIAM L. WALKER, OF NEW YORK, N. Y., ASSEGNOR TO WALKER SIGNAL 85 EQUIP- MENT" COR0RATION3 OE'NEW YORK, N. Y", A CORBORATION 0F DELAVARE.

MICROPHONE.

Application filed- August 12, 1921. SeriaLNo. 4=S1,'?15.

To all whom, it may concern:

Be it known that 1, WILLI M L. WALKER,

a citizen of the United States, residing in the borough-of Manhattamcity, county, and State of blow York, have invented :certain new and useful Improvements in Microphones, of which the :t'ollmvingis a full,

cleaigconcise, and exact description.

h'ly invention relates particularlyto microphones for, receiving and transmitting sound vibrations and. is particularly adapted tothe transmission of sound .waves; received through liquid. media such as water, to telephones either directly or throughamplifying devices now often used and well known in the art. My apparatus is particularly adapted to receive vibrations produced by submarine sound signaling devices and transmit the same to those aboard warships or other vessels whereby navigational or military information may be utilized.

The present microphones now in use are ill-adapted for use in submarine signaling on account of the great difficulty of being accurately aatched and retaining their matched qualities, this being the primary requ ite. for obtaining accurate directive results. V

For use in receiving submarine signals or sounds, microphones should be very ruggedly constructed, capableof being readily matched, of great durability and not liable to transmit variations except 'thoseimpressed directly on the diaphragm, that is, lateral vibrations originating within the ship itself and communicated tothe skin of the vessel should affect the microphones to the very smallest degree; Furthermore, microphones used for submarine:signaling must he very uniform in their action and possess a standard degree oil" effectiveness which must be continuouslymaintained and not sub-fleet to variationror deterioration. here microphones are used on oppositc sides of a vessel fo-r the purpose of indicating the direction of the'sou-rceflofsound, the microphones must be -of';substantially equal action or responsiveness to the sound-waves and 'must maintains-these characteristics to obtainsatisfactory results-.:

All microphones now in use to a considerable extent in submarine-signaling contain carbon particles and-have-inica diaphragrns.

".LheSe, however, are not entirely satisfactory for submarine signaling on account of being fragile and unstable in their nature, owing to the use of parts which do not give uniformly variable resistance at the resistance varying points. On the contrary, the use of my improved microphone obviates these did'eulties and the construction enables the microphones to bemade substantially of one standard. effectiveness or resultant action in converting the sound waves into corresponding electric waves to be transmitted to the telephone receiver.

l f-rieily stated, my improved microphone involves the use of a. series of preferably thin carbon discsor plates placed taco to face and under slight pressure bet-ween electrical conducting pieces or plates which preferably have pointed surfaces to give better microphonic contacts for the transmission of the current to the carbon discs or plates. The planes of he carbon discs referred to are preferably arranged parallel to the "face or the receiving (1' iphragm so that lateral vibrations, that is, vibrations in the direction 026 the plane of the diaphragm or parallel thereto in the supporting parts, are not communicated to the discs in the direction of their axes. These carbon discs may be made of uniform thickness, hardness, size and fineness of the carbon, thereby enabling the action of the microphones to be renderedsubstantially uniform and constant as regards the conversion of the sound wavesso as to cause similar variable resistances and thereby produce correspond-- ingly variable electric. currents. more, by varying the pressure of the respective carbon discs or -their size and'number, the respective microphones in a signal receiving installation can be set for any required resistance, current, and tone quality, which will enable them to receive in the most eiii-cien-t manner a desired signal or sound and thosemost suitable for the particular type of the telephones or amplifying devices which. may be desired to be used in connection therewith. The use-of carbon discs under resilient pressure has been found toelin iinate noises sometimes produced in other sensitive microphones whetherused with or without amplifying tubes, particularly the so-ealled trying sound, which is produced when the; microphone energizing:- current of certain strengths- Furtheras produced by apparatus used'in sound signaling, that is, by designingthe diaphragm, the connecting parts and the number and size of the carbon-discs, the micro phone can be made to respond more perfect- 1y to submarine signals of standard fre quency than to undesirable sounds caused by the water or noises originating aboard the ship, and thus the selectiveness or tuning ofthe microphone can be brought about to a high degree. The construction here1nafter described also results in a microphone that is very rugged and will stand a great deal of abuse withoutv having its soundelectrical-converting properties affected .or changed to any substantial degree, in con sequence of which the mircrophone is unusually reliable and constant in its action at all times. 7

Therefore, when separate microphones are constructed similarly with similar electric characteristics they will have the same action or efl'ect,therebeing no loose particles or grains or material to become displaced and thereby cause variable results.

Furthermore, my improved microphone can be made as sensitive as any microphone available at the present time, or may be damped to almost any degree by varying the number and size of the plates or discs or the pressure thereon.

From the foregoing description, it will be seen since the microphones can be made with very uniform operating characteristics, they can easily be matched, especially when used accumulatively, that is, when used in series or in parallel they will augment the received sound signals practically in 'proportion to the number connected together.

The simplicity of construction of this microphone is such that any parts subject to injury or wear can be easily replaced antl the same characteristics obtained as before being damaged.

I have found that this microphone reproduces speech or sounds with'practicallytrne I tone or quality and furthermore the quality of tone is not affected by amplification.

Although I have referred to this'microphone as being particularly adapted for use in submarine signaling, it is obvious that it can be used equally well for other purposes and where other forms'of microphones have been used. c

The preferred form of my invention is described in the followingspecification and of the water as the -5 and made as light as small holes therethrough.

reference is made therein to the accompanying drawings forming a part thereof, in which:

Fig. 1 is a longitudinal sectional view of one form of my improved "microphone, at tached to a diaphragm as disclosed. in my previous patent application, Serial No. 468,611, filed the 11th day of May, 1921.

Fig. 2 is an enlarged sectional view of the tube for supportingthe carbon plates or discs and contact plates of-the microphone, showing the details thereof.

Fig. 3 is an end view of microphone tube and cap.

Fig. 4- is a plan-view of one of the contact plates between which the carbon discs are held. Y

Fig' 5 is a diametral sectional view of the contact .plate of Fig. 4. I

Referring to the drawing, the numeral 1 indicates a. circular ring made of steel or similar resilient material preferably having the diaphragm 2 made integral therewith. This ring and diaphragm are applied to the circular opening in the side or skin of a vessel bymeans of suitable flanged rings secured in position by bolts as indicated.

The diaphragm 2 is so positioned to be,

flush with the outer surface of the side of the vessel thereby forming a part of the stream line surface of the hull and prevent ing sounds caused'by eddy currents, and similar noises caused by local disturbances vessel travels through the same.

filed 11th day of May, 1921.. jection or boss 3 is formed at the center of the diaphragm 2 and has a central screw threaded recess. adapted to receive one end of a' small screw-threaded pin 4 carrying on'its' opposite end a cup-shaped receptacle 5 which parts are preferably'made of a metallic 'material The small I cup-shaped member constitutes a socket which receives one end of a small insulation member 6 in the form of a cylindrical rod of condensation product of phenol or other insulating material, the op posits-end of which enters a socket inthe boss 7 carried by a disc 8. The opposite surface of the disc 8 is preferably pointed or roughened as indicated at 8' in Figs, 4 and possible by boring This surface is preferably formed by cutting transverse grooves at right angles to each other through the use of a milling cutter and the holes referred to are drilled at the bottom of the intersections of the grooves as clearly indicated in Fig. 4, but may be made in other ways.

As a support for the other parts constituting' the active portions of the microphone exclusive of plate 8 a cylindrical tube This construction is disclosed in my said application, Serial No. 468,611, A small pro such asbrass, steel, etc. c

nw'sgase 9'is'. provided, preferably made of insulating material or ifnot insulating then havan insulating layer on its interior surface. This-surface should-be smooth and free from any tendency to retard the free movement of the carbon discs. The tube 9 is supported in an internally screw-threaded ring 10 and is provided with an hexagonal flange 9 which. abuts against said. ring .10 and fixes the tube 9 in position. The ring 10 issupported by a plate 11 of material which ispreferably flexible but non-elastic. Forthis purpose, I have found that ant-(1+ terial resembling rubber coated cot-ton packing orbcltihgismost desirable. This materail is substantially waterproof, very durable,rand non-resilient to a high degree. Through its use, .I' am enabled to prevent lateral vibrations transmitted by the skin of .the vessel being communicated to the sup porting. tube 9 containingrthe carbon'discs constituting the-microphone proper. This v plate isat tached to tlic'supp'orting ring 10 til) in any suitable :way such as by annular rings 12 to which the ring 10 is secured by means of machine screws 13, or equivalent device; The out-er margin of the plate 11 is attached to the annular plate 14 which is clamped between the ring'l and the clamping ring 15.

Referring now to the parts within the supporting tube 9-(Fig. 2), a series ofcarhon discs 16 are seton edge or vertically arranged within the tube, the first one contacting with the roughened-o1poin-ted plate 8' and the last one contacting with a similarly pointed plate 17; This plate is provi'ded with an outwardly extending lug 18 which receives the end of an insulated wire 19, which passes through the cap 20. The cap- 20 is interiorly screw-threaded and adapted to engage the screw threads on the outer surface of the tube 9 and is provided with a series of longitudinal grooves 21 adapted to receive a rib 22 carried on the resilient arm 23 attached to the flange 9 of the tube 9. The rib 22 engaging the grooves 21, holds the cap 20 in any radial position without becoming loosened by vibrations or shocks transmitted to the tube. Between the interior surface of the cap 20 and the plate 17, I insert the resilient pressure member which may be in the form of a spring or other well known part, as indicated by the numeral 24. This may be placed under compression by adjusting the position of the cap 20 and so produce a definite pressure between the series of carbon discs 16 as will be readily appreciated by considering Fig.

The electrical connections for introducing energizing current for the n'iicrophone may be conducted to the contacting parts in any suitable way, such as by the wire 25 passing through the plate 11, which wire enters the space between said plate and the diaphragm and is attached to the socket 7 on the disc 8. The other terminal 19 may pass throughthe cap 20 and engage the lug 1S, as-above described, or in any other suit able manner.

Asabove indicated, platesS'and 17, which ar'ein contact with the opposite ends respectively of-the series-of carbon discs and under compression by the spring 2%, each have similar contacting surfaces engaging the carbon discs; These surfaces are grooved, roughened, or othewise formed so as to have a-plurality of individual projecttions for conducting the electrical current to the carbon resistance element.- The functionof the sharp pyramidal points is to make a multiple microphonic contact with the-carbon discs, as distinguished from a sin gle electricalcontact. In practice I have found-thatby properly adjusting the compressionof the spring contacts(described, the sensitiveness of the microphone is greatly increased.

From a consideration ofuthe above description, taken in connection with the drawing, the operation of my improved microphone will be apparent without further explanation and the advantages set forth prior to the detailed description will readilybe recognized. I do not wish to be understood asbcinglimi-ted to the; details o f form or arrangement of parts herein sot fortlr, for various changes may be madcby' those skilledin the art without departing from the spirit or scope of my invention...

hat I claim and desire to protect by Letters Patent is:

1.111. a microphone, a current varying member comprising a body of laminated carbon,- and metallic plates having numerous definitely preformed contacting points thereon and adapted to contact with opposite ends of said body for conducting electric current into and through said body.

2. In a microphone, a current varying member comprising a body of laminated carbon and conducting plates having numerous definitely preformed points thereon contacting with the opposite ends of said body for conducting electric current into and through said body.

3. In a microphone, a current *arying member comprising a series of thin carbon discs in contact with each other and bearing plates having numerous definitely preformed points thereon in Contact with said discs at each end of said series for conducting electric current into and through said plates.

4. In a microphone, acurrent varying member comprising a body of compressed homogeneous pieces of carbon, and recessed bearing plates providing numerous projections contacting with the opposite sides of said pieces.

A microphone comprising a series of conductive current varying elements and opand using the point 7 contacting with. the outer posed conducting parts having a plurality of minute definitely preformed contacting points engagingthe outer elements of said series.

6. A microphonecomprising a series of conductive current varying elements and including conducting parts having a series of sharp points contacting with adjacent elements of said series. 7 '7. A microphone comprising a series of conductive current varying elements in the form of successive plates, opposed conduct-' ing parts having a series of sharp points contacting with the outer elements of said series, and means for producing resilient pressure on said elements between said parts.

8. A microphone comprising a series of conductive current varying elements in the form of successive plates, opposed conducting parts having a series of sharp points contacting withtheouter elements of said series,'a resilient member" engaging one of said parts, a tubefin which said; member, parts and elements are contained, and {mad justable cap engaging the end. of said tube and said resilient member and adapted to determine the pressure on said elements.

9; A microphone comprising, a series of conductive current varying elements in the form of successive plates, opposed conducting parts having a'series of sharp points elements of said series, a resilient member contacting with one of said parts, 'aninsulating tube in which said "member, parts and elements are contained, means for varying the compres sion'of said resilient member, and an insulating connector for uniting the other of said parts with the diaphragm of said micro phone.

sure between said elements and means for holding said cap in various positions axially. 11. A microphone comprising, a. diaphragm, a hollow container, a series of conductive current varying means for operatively connecting said' diaphragm and said elements, means for transmitting electric current .to'andthrough said a series of sharp points elements therein,

elements, and afiexible non-resilient supr.

porting member carrying said container and adapted to confine the vibrations active upon said-elements to those substantially normal to the said diaphragm. I

12. A microphone comprising, a series of conductive current varying elements in the form of successive sheets or plates, means for transmitting electric current to and through said elements, a supporting tube, therefor,

and a flexible non-resilient supporting extending I laterally from adapted to hold the latter in plate said tube and position and to 'confine'the active vibrations to those substantiallynormal to the diaphragm of the microphone.

" WILLIAM WALKER 

